std::is_null_pointer

Defined in header `<type_traits>`
template< class T > struct is_null_pointer;		(since C++14)

Checks whether T is the type std::nullptr_t.

Provides the member constant value that is equal to true, if T is the type std::nullptr_t, const std::nullptr_t, volatile std::nullptr_t, or const volatile std::nullptr_t.

Otherwise, value is equal to false.

Inherited from std::integral_constant

Member constants

value

[static]

true if T is the type std::nullptr_t (possibly cv-qualified) , false otherwise
(public static member constant)

Member functions

operator bool	converts the object to bool, returns `value` (public member function)
operator() (C++14)	returns `value` (public member function)

Member types

Type	Definition
`value_type`	`bool`
`type`	std::integral_constant<bool, value>

[edit] Notes

std::is_pointer is false for std::nullptr_t because it is not a built-in pointer type.

[edit] Example

Run this code

#include <iostream>
#include <type_traits>
 
int main()
{
    std::cout << std::boolalpha
              << std::is_null_pointer< decltype(nullptr) >::value << ' '
              << std::is_null_pointer< int* >::value << '\n'
              << std::is_pointer< decltype(nullptr) >::value << ' '
              << std::is_pointer<int*>::value << '\n';
}

Output:

true false
false true

[edit] See also

is_void (C++11)	checks if a type is void (class template)
is_array (C++11)	checks if a type is an array type (class template)
is_pointer (C++11)	checks if a type is a pointer type (class template)
is_enum (C++11)	checks if a type is an enumeration type (class template)
is_union (C++11)	checks if a type is an union type (class template)
is_class (C++11)	checks if a type is a class type (but not union type) (class template)
is_function (C++11)	checks if a type is a function type (class template)
is_object (C++11)	checks if a type is object type (class template)
std::experimental::is_null_pointer_v (library fundamentals TS)	variable template alias of `std::is_null_pointer::value` (variable template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Technical Specifications

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
Relational operators
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Pairs and tuples
pair
tuple (C++11)
piecewise_construct_t (C++11)
piecewise_construct (C++11)
integer_sequence (C++14)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
declval (C++11)